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syeshinbefd53e2005-07-27 18:16:40 +0000[diff] [blame]17<title>XML file associations with DTDs and XML schemas</title>
syeshin66078272005-09-20 16:53:38 +0000[diff] [blame]18</head>
syeshinbefd53e2005-07-27 18:16:40 +0000[diff] [blame]19<body id="cxmlcat"><a name="cxmlcat"><!-- --></a>
20
21<h1 class="topictitle1">XML file associations with DTDs and XML schemas</h1>
syeshind0bdb8e2005-10-27 17:44:14 +0000[diff] [blame]22<div><p>When an XML file is associated with a DTD or XML schema, it is
23bound by any structural rules contained in the DTD or XML schema. To be considered
24a valid XML file, a document must be accompanied by a DTD or an XML schema,
25and conform to all of the declarations in the DTD or the XML schema.</p>
syeshinbefd53e2005-07-27 18:16:40 +0000[diff] [blame]26<div><p>There are two different ways to associate XML files with DTDs or
27XML schemas.</p><ol><li>Direct association - The XML file contains either the name of a DTD in
28its doctype declaration (for example, &lt;!DOCTYPE root-element SYSTEM " <var class="varname">dtdfile.dtd</var>"
29&gt;, where <var class="varname">dtdfile.dtd</var> is the name of the DTD file) or it
30contains the path of an XML schema in the schemaLocation attribute of the
31XML file root element (for example, &lt;xsi:schemaLocation="http://www.ibm.com
32 <var class="varname">schema.xsd</var>"&gt;, where <var class="varname">schema.xsd</var> is
33the name of the XML schema.</li>
syeshind0bdb8e2005-10-27 17:44:14 +0000[diff] [blame]34<li>XML Catalog entry - You can register DTD and XML schema files in
syeshinbefd53e2005-07-27 18:16:40 +0000[diff] [blame]35the XML Catalog and associate them with a <var class="varname">Key</var> that represents
36them. You can then refer to a DTD or XML schema file <var class="varname">Key</var> from
37an XML file instead of referring directly to the DTD or XML schema file. An
38XML Catalog entry contains two parts - the Key (which represents the DTD or
39XML schema) and a URI (which contains information about the DTD or XML schema
40location).</li>
41</ol>
syeshind0bdb8e2005-10-27 17:44:14 +0000[diff] [blame]42<div class="skipspace"><h4 class="sectiontitle">How an association works</h4><b>Associating an XML
syeshinbefd53e2005-07-27 18:16:40 +0000[diff] [blame]43file with a DTD </b><div class="p">If an XML file is associated with a DTD, a DOCTYPE
44tag such as the following is included in the XML file:<pre>&lt;!DOCTYPE root-name PUBLIC "<var class="varname">InvoiceId</var>" "<var class="varname">C:\mydtds\Invoice.dtd</var>"&gt;</pre>
45</div>
46<p><var class="varname">InvoiceId</var> is the public identifier of
47the DTD file. It is used to associate the XML file with a DTD file (in this
48case, the DTD file is <var class="varname">Invoice.dtd</var>). If the public identifier
49InvoiceId corresponds to the <var class="varname">Key</var> of the XML Catalog entry
50for Invoice.dtd, then the <var class="varname">URI</var> of the XML Catalog entry
51(which contains information about the location of Invoice.dtd) is used to
52locate the DTD. Otherwise, the DOCTYPE's system identifier ( <var class="varname">"C:\mydtds\Invoice.dtd"</var>),
53which refers directly to the file system location of the DTD, is used to locate
syeshind0bdb8e2005-10-27 17:44:14 +0000[diff] [blame]54the DTD.</p>
syeshinbefd53e2005-07-27 18:16:40 +0000[diff] [blame]55<p> <b>Note</b>: You can also use a system identifier as
56a Key in an XML Catalog entry. If you use a system identifier as a Key, a
57DOCTYPE tag such as the following is included in an XML file:</p>
58<pre>&lt;!DOCTYPE Root-name SYSTEM "<var class="varname">MyDTD.dtd</var>"&gt; </pre>
59<p>where <var class="varname">MyDTD.dtd</var> is the system identifier that corresponds
60to the Key of an XML Catalog entry.</p>
61</div>
62<div class="skipspace"><b>Associating an XML file with an XML schema</b><p>If an XML file
63is associated with an XML schema, one or more schema location attributes are
64included in the XML file. The information in the schemaLocation is provided
65as a "hint" to the XML processor. Examples of schemaLocation attributes are
66shown below: </p>
67<div class="p"> <b>Example 1 </b><pre>&lt;purchaseOrder xmlns="http://www.ibm.com"
68xsi:schemaLocation="http://www.ibm.com C:\myschemas\PurchaseOrder.xsd"&gt;
syeshind0bdb8e2005-10-27 17:44:14 +0000[diff] [blame]69&lt;shipTo country="US"&gt;
syeshinbefd53e2005-07-27 18:16:40 +0000[diff] [blame]70...</pre>
71 </div>
72<div class="p"><b>Example 2 </b><pre>&lt;purchaseOrder xmlns="http://www.ibm.com"
73xsi:schemaLocation="http://www.ibm.com PO.xsd"&gt;
syeshind0bdb8e2005-10-27 17:44:14 +0000[diff] [blame]74&lt;shipTo country="US"&gt;
syeshinbefd53e2005-07-27 18:16:40 +0000[diff] [blame]75....</pre>
76 </div>
77<p>In Example 1, the schemaLocation 'hint' ('C:\myschemas\PurchaseOrder.xsd')
78refers directly to the file system location or URI of the XML schema. In this
79case, the schema file will be located by the XML processor directly.</p>
80<p>In
81Example 2, the schemaLocation 'hint' ('PO.xsd') refers to an XML Catalog entry.
82PO.xsd corresponds to the <var class="varname">Key</var> of the XML Catalog entry
83for PurchaseOrder.xsd, and the URI of the XML Catalog entry (which contains
84information about the location of PurchaseOrder.xsd) will be used to located
85the XML schema.</p>
86<p>In both examples, <samp class="codeph">http://www.ibm.com</samp> in
syeshind0bdb8e2005-10-27 17:44:14 +0000[diff] [blame]87the <samp class="codeph">xsi:schemaLocation</samp> tag is a URI that identifies
88the namespace for the XML schema.</p>
syeshinbefd53e2005-07-27 18:16:40 +0000[diff] [blame]89<div class="p">You can also use a namespace as a Key for
90an XML Catalog entry. If you use a namespace as a Key, a schemaLocation tag
syeshind0bdb8e2005-10-27 17:44:14 +0000[diff] [blame]91such as the following is included in an XML file:<pre>&lt;purchaseOrder xmlns:="www.ibm.com&quot;
92xsi:schemaLocation="http://www.ibm.com po/xsd/PurchaseOrder.xsd "&gt;</pre>
syeshinbefd53e2005-07-27 18:16:40 +0000[diff] [blame]93</div>
94<p>The
95schemaLocation attribute points to both the Key and the actual location of
96the schema.</p>
97<p><b>DTD or XML schema resides on a remote server</b></p>
98<p>Several
99functions in the XML editor, such as validation and content assist, require
100the availability of a DTD or an XML schema. The product documentation provides
101usage information for cases when the DTD or XML schema resides on your local
102machine. However, in many cases, the DTD or XML schema may reside on a remote
103server, for example:</p>
104<p><samp class="codeph">&lt;!DOCTYPE Catalog PUBLIC "abc/Catalog"
105"http://xyz.abc.org/dtds/catalog.dtd"&gt;</samp></p>
106<p>Normally, this case
107poses no problem, because the DTD or XML schema can be retrieved from the
108remote server. However, if you are behind a firewall, and do not have a SOCKSified
109system, the workbench currently does not provide a way for you to specify
110a socks server for retrieving a DTD or XML schema. If you are unable to SOCKSify
111your system, the workaround for this problem is to retrieve a copy of the
112DTD or XML schema (using a Web browser, for example) and save that copy on
113your local machine. Then, you can either place a local copy in the same project
114as your XML file, or use the XML Catalog to associate a public identifier
115with the DTD's (local) location.</p>
116<p><b>Note</b>: If you have an XML file
117associated with an XML schema or DTD that is elsewhere in the network, and
118you are working on a machine disconnected from the network, you can follow
syeshind0bdb8e2005-10-27 17:44:14 +0000[diff] [blame]119the steps described previously if you want to use content assist or validate
120your XML file. </p>
syeshinbefd53e2005-07-27 18:16:40 +0000[diff] [blame]121</div>
122<div class="skipspace"><h4 class="sectiontitle">Advantages of XML Catalog entry associations</h4><p>If
123you create a direct association between an XML file and an XML schema or DTD
124file, any time you change the location of the schema or DTD you have to track
125down and update all of the referencing XML files with the new location of
126the DTD or schema. If, however, you associate an XML file with an XML schema
syeshind0bdb8e2005-10-27 17:44:14 +0000[diff] [blame]127or DTD Key, then, when you change the location of the schema or DTD, you only
128 have to update the XML Catalog entry, instead of each individual XML file.</p>
syeshinbefd53e2005-07-27 18:16:40 +0000[diff] [blame]129<p>For
130example, you have a DTD called "Building.dtd", which is associated with five
131XML files - Office.xml, House.xml, Apartment.xml, Bank.xml, and PostOffice.xml.
132You move the DTD file Building.dtd to a new location. If you have a direction
133association between Building.dtd and all the XML files, you will have to update
134the &lt;DOCTTYPE&gt; declaration in each XML file to reflect the new location
syeshind0bdb8e2005-10-27 17:44:14 +0000[diff] [blame]135of Building.dtd. If, however, you have an XML Catalog association, and
syeshinbefd53e2005-07-27 18:16:40 +0000[diff] [blame]136all the XML files just refer to the Key of Building.dtd, then you only have
137to update the URI and all the XML files will point to the new location of
138Building.dtd.</p>
139</div>
140<div class="skipspace"><h4 class="sectiontitle">Updating an entry in the XML Catalog</h4><p>After you have
141updated an entry in the XML Catalog, you may need to refresh the XML editor
142view so that it uses the new information. To do this, click the <span class="uicontrol">Reload
143Dependencies</span> toolbar button <img src="../images/rldgrmr.gif" /> and
144the view will be updated using the current XML Catalog settings. You only
145need to refresh the XML editor view when you have an XML file open that references
146the XML Catalog entry that was updated.</p>
147<p>For more information, refer
148to the related concepts and tasks below.</p>
149<p>(c) Copyright 2001, World Wide
150Web Consortium (Massachusetts Institute of Technology, Institut National de
151Recherche en Informatique et en Automatique, Keio University).</p>
152</div>
153</div>
syeshind0bdb8e2005-10-27 17:44:14 +0000[diff] [blame]154<div><div class="relconcepts"><strong>Related concepts</strong><br />
155<div><a href="../topics/cwxmledt.html" title="The XML editor is a tool for creating and viewing XML files.">XML editor</a></div><br/>
156<div><strong>Related tasks</strong><br/>
157 <a href="../topics/tedtcnst.html" title="In the Design view, when you edit an XML file that has a set of constraints (that is, a set of rules) defined by a DTD or an XML schema, you can turn the constraints on and off to provide flexibility in the way you edit, but still maintain the validity of the document periodically.">
158 Editing with DTD or XML schema constraints</a></div>
159 <div>
160 <a href="../topics/tedtdoc.html" title="The DOCTYPE declaration in an XML file is used at the beginning of it to associate it with a DTD file. You can edit your DOCTYPE declaration to change the DTD file your XML file is associated with.">Editing DOCTYPE declarations</a></div>
161 <div>
162 <a href="../topics/txmlcat.html" title="An XML Catalog entry contains two parts - a Key (which represents a DTD or XML schema) and a Uniform Resource Identifier (URI) (which contains information about a DTD or XML schema's location).  You can place the Key in an XML file. When the XML processor encounters it, it will use the XML Catalog entry to find the location of the DTD or XML schema associated with the Key">Adding entries to the XML Catalog</a></div>
163 <div>
164 <a href="../topics/tedtgram.html" title="If you make changes to a DTD file or XML schema associated with an XML file (that is currently open), click XML &gt; Reload Dependencies to update the XML file with these changes. The changes will be reflected in the guided editing mechanisms available in the editor, such as content assist.">Updating XML files with changes made to DTDs and schemas</a></div>
165 <div>
166 <a href="../topics/tedtsch.html" title="Your namespace information is used to provide various information about the XML file, such as the XML schema and namespace it is associated with. If desired, you can change the schema and namespace your XML file is associated with or add a new association. Modifying any associations can impact what content is allowed in the XML file.">Editing namespace information</a></div>
167 <div>
168 <a href="../topics/tedtproc.html" title="If you have instructions you want to pass along to an application using an XML document, you can use a processing instruction.">Editing XML processing instructions</a></div>
169 <div>
170 <a href="../topics/txedtdes.html" title="The XML editor has a Design view, which represents the XML file simultaneously as a table and a tree. This helps make navigation and editing easier. Content and attribute values can be edited directly in the table cells, while pop-up menus on the tree elements give alternatives that are valid for that particular element.">Editing in the Design view</a></div>
171 <div>
172 <a href="../topics/txedtsrc.html" title="You can use the Source view to view and work with a file's source code directly.">Editing in the Source view</a></div>
syeshinbefd53e2005-07-27 18:16:40 +0000[diff] [blame]173</div>
syeshind0bdb8e2005-10-27 17:44:14 +0000[diff] [blame]174</div></body>
syeshinbefd53e2005-07-27 18:16:40 +0000[diff] [blame]175</html>